Preparation Of Hollow Carbon Spheres@Co₃O₄ Based On Cross-linked Poly（Divinylbenzene-maleic Anhydride） Hollow Microspheres

Cross-linked polymer hollow microspheres are light and have a large specific surface area.Nanomaterials with a small particle size are widely used.However,they are very easy to agglomeration.Using polymer hollow microspheres to load nanomaterials can play a synergistic role,which has an important practical significance.This thesis mainly studies the preparation method of hollow carbon sphere@Co3O4 material based on hollow polymer microspheres prepared by self-stable precipitation polymerization.The hollow polymer microspheres were prepared by self-stable precipitation polymerization,the surface of the hollow polymer microspheres was modified,and then the hollow carbon sphere@Co3O4 material was obtained by in-situ generation method.The main contents and contributuion of this thesis are as follows:First,the core-shell polymer microspheres were synthesized by self-stable precipitation polymerization in one pot.The polymer core was poly(styrene-maleic anhydride)(PMS)and the shell was cross-linked poly(divinylbenzene-maleic anhydride)(DVB-MAH),then acetone is used to remove the PMS template to obtain hollow cross-linked poly(divinylbenzene-maleic anhydride)microspheres(HPPs)By adjusting the ratio of monomers and the type of crosslinking agents(DVB55 and DVB80),their morphology and particle size were optimized,and HPPs with core-shell ratios of 1:1,1:1.25,1:1.5,and 1:1.75 were synthesized.The morphology was characterized by SEM and TEM,and HPPs with good morphology and particle size were selected in following study.The results show that the amount and type of cross-linking agent will affect microsphere morphologyand shell thickness.HPPs with a core-shell ratio of 1:1 and 1:1.25 synthesized using the cross-linking agent DVB55 have good morphology,and the average particle size is about 610 nm and 656 nm.They have uniform particle size,and the average shell thickness is about 100 nm.Second,hydrolysis,amination,sulfonation,and N-β-hydroxyethyl ethylenediamine triacetic acid(HEDTA)were used to modify the HPPs with a core-shell ratio of 1:1 and 1:1.25 synthesized with DVBss.After surface modification,HPPs-COOH,HPPs-NH2,HPPs-HSO3 and HPPs-HEDTA are obtained.SEM results showed that the morphology of HPPs-COOH,HPPs-HSO3,HPPs-HEDTA microspheres were partially damaged,and the morphology of HPPs-NH2 microsphere did not change much.The average particle size of the four surface-modified microspheres increased relative to HPPs.It can be seen from the TEM image that the hollow structure of the microspheres remains intact after four different surface modifications.Compared with HPPs with a core-shell ratio of 1:1,HPPs with a core-shell ratio of 1:1.25 perform better after surface modification.The average particle diameter is about 775 nm,and the average shell thickness is about 100 nm.Third,using the above-mentioned HPPs-COOH,HPPs-NH2,HPPs-HSO3 and HPPs-HEDTA with a core-shell ratio of 1:1.25 as the reaction matrix,Co3O4 nanoparticles were synthesized in situ on the surface of the hollow microspheres.Polymer microspheres and Co(NO3)2·6H2O aqueous solution was mixed to adsorb Co2+ on the surface of the microspheres,and then they were calcined twice,including being calcined at 600℃ for 2 h under nitrogen atmosphere,and then being calcined at 300℃ for 2 h under air atmosphere.The obtained microsphere-nanoparticle composites with different surface modifications are denoted as HCSs-COOH@Co,HCSs-NH2@Co3O4,HCSs-HSO3@Co3O4 and HCSs-HEDTA@Co3O4.Through XRD test,it was found that the surface modification of microspheres have an effect on the crystal form of the nanoparticles.HPPs-NH2,HPPs-HSO3 and HPPs-HEDTA were loaded with Co2+ and then calcined twice to successfully load Co3O4 particles,while HPPs-COOH gave Co particles.It can be seen from the SEM and TEM images that the morphology of HCSs-NH2@Co3O4 after two calcinations is maintained,the hollow structure is intact and the loading of Co3O4 particles is uniform.Four,for HPPs-NH2 microspheres,1,2 and 3 mg/ml of Co(NO3)2·6H2O solutions were used for Co2+loading,and the final microspheres were characterized by XRD,SEM,TEM,FT-IR and XPS to determine the phase,morphology,chemical structure and chemical composition.Taken together,the HCSs-NH2@Co3O4 with different concentrations of Co2+ solution has a good surface morphology.With increasing concentration of Co2+ solution,the loading of Co3O4 nanoparticles shows an upward trend.Hollow polymer microspheres loaded with nanomaterials can exert the synergy of the two,and have great application prospects in the field of catalysation,drug controlled release,and enzyme immobilization.